BIZOMAT MAKEOS · Manufacturing
Speeds and Feeds in Inch Units
What spindle speed and feed rate follow from this SFM and chip load?
Spindle speed from surface feet per minute and diameter, and feed rate from inches per tooth (or per revolution), with metric equivalents.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Surface speed | ft/min | Recommended surface feet per minute for the tool and material. |
| Cutter or work diameter | in | Effective cutting diameter in inches. |
| Number of teeth (1 for turning or drilling per rev) | teeth | Flutes or inserts on the cutter; 1 when the feed is per revolution. |
| Feed per tooth (or per rev) | in | Chip load per tooth (or feed per revolution for turning and drilling). |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Surface speed
- What it is
- The cutting speed at the tool edge in surface feet per minute, as recommended by the tool maker for the tool and work material.
- Units and format
- Enter a number in ft/min: ft/min. The form accepts 0.000001 ft/min to 100000 ft/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 400 ft/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Spindle speed and feed rate rise in proportion to surface speed.
- Get it right
- Take it from the cutting tool supplier’s data for the material; it is a surface speed, not a spindle speed.
What this means: Cutter or work diameter
- What it is
- The diameter at the cutting edge: the cutter diameter for milling and drilling, or the work diameter being cut for turning.
- Units and format
- Enter a number in in: inches. The form accepts 0.000001 in to 1000 in. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.5 in as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Spindle speed falls in inverse proportion to diameter.
- Get it right
- Enter inches. For a ball-nose cutter at shallow depth, use the effective diameter in contact.
What this means: Number of teeth (1 for turning or drilling per…
- What it is
- The number of cutting edges (flutes or inserts) that each take a chip per revolution; one when the feed is given per revolution.
- Units and format
- Enter a number in teeth: a whole number of teeth. The form accepts 1 teeth to 500 teeth. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4 teeth as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The feed rate rises in proportion to the number of teeth.
- Get it right
- For turning or drilling with a per-revolution feed, enter one.
What this means: Feed per tooth (or per rev)
- What it is
- The chip load each tooth removes per revolution, or for turning and drilling the feed per revolution, from the tool maker’s data.
- Units and format
- Enter a number in in: inches. The form accepts 0.000001 in to 1 in. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.002 in as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The feed rate rises in direct proportion.
- Get it right
- Per tooth and per revolution differ by the number of teeth; match this value to the teeth input.
Method and formulas
- RPM = 12 × SFM ÷ (π D) ≈ 3.82 × SFM ÷ D.
- IPM = RPM × teeth × IPT.
- Metric: m/min = SFM × 0.3048; mm/min = IPM × 25.4.
- Example: 400 SFM on a 0.5 in cutter is 3,055.8 rpm; at 0.002 in/tooth with 4 teeth the feed is 24.446 in/min.
Limitations
- Supplier recommendations govern; check machine speed and power limits.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Convert supplier SFM and IPT data to machine settings
- Check inch programs
- Work with US tooling catalogues
Who it is for
- Machinists
- CNC programmers
- Manufacturing engineers
What you get
- Spindle speed
- Feed rate
- Metric equivalents
Interpreting the result
- Round the RPM to the nearest available speed and recompute the feed.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1013–1017. Topic reference; no source tables or recommended settings are reproduced.
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